Heriades variolosa

Taxonomy

Heriades variolosa is in the family Megachilidae. Bees in the genus Heriades are sometimes known as “resin bees” because they use resin instead of leaf tissues to build their nests. There are only 3 species known to live in Minnesota. The majority of our specimens are H.carinata, but in 2017 we had nests of both H. leavitti and H. variolosa as well. Heriades variolosa was an uncommon bee in Bee Atlas blocks, and all nests were in western Minnesota, in the Prairie Parklands prvin.

Description

Heriades variolosa is a fairly small bee, a little smaller than Osmia pumila. Their exoskeletons are all black with less hair and more coarsely sculpted exoskeletons than many other bees. They are robust, but thinner, with a more cylindrical body form compared to Megachile spp., which frequently have abdomens that appear somewhat broad and flattened. Heriades have white bands across the abdomen, and their abdomens frequently appear to curl downward. The females collect pollen in a scopa, or pollen brush, under the abdomen, like all nest-building Megachilidae. Scopal hairs and many body hairs appear very light or white.

Nest Structure

Heriades use resin to build internal nest walls and nest plugs (see graph). Resin plugs may be light or dark, with or without debris stuck into them. Resin plugs can be distinguished from other plugs because they are either tacky or rock hard, not papery or flexible. Sometimes if you press lightly with your fingernail you can see an indent left in the newer tacky plugs, and you may even notice a "piney" smell.

Hole Sizes

Heriades variolosa most frequently nested in upper column 3 holes (1/8"), and also nested in lower column 3 holes (3/16") in Bee Atlas blocks. (see graph in pictures)

Voltinism

Univoltine, meaning they complete one generation per year in Minnesota.

Activity Period

Between 2016-2018, nest completion was recorded between the middle of July and the middle of August. However, we had a relatively small number of nests in this project. 

References

No information at this time.